Project Summary/Abstract Pyruvate kinase M2 (PKM2) is primarily a tetrameric enzyme that catalyzes the transfer of a phosphate from phosphoenolpyruvate to ADP, resulting in pyruvate and ATP. PKM2 is abundant during embryogenesis and in specific adult tissues such as adipose and pancreatic islets. New evidence suggests that PKM2 expression in these tissues may have a pivotal role in regulating glycolysis, cell death, and proliferation. However, the metabolic functions of PKM2 in these tissues remain largely unexplored. Our preliminary data shows that PKM2 deficiency improved differentiation of 3T3-L1 pre-adipocytes into mature adipocytes and enhanced mitochondrial respiratory capacity. Moreover, PKM2 deficiency in white adipocytes activated a brown fat-like gene program, which translated into increased mitochondria biogenesis and expression of UCP1, BMP7, and PRDM16. To further delineate PKM2 metabolic functions we will employ complementary approaches. First, we will use a cell platform to investigate the metabolic functions of adipose PKM2 ex-vivo and dissect the underlying mechanisms. Then, we will determine the metabolic role of adipose PKM2 in vivo using two approaches: (1) a genetic approach using mice with adipose-specific deletion by crossing adipose-specific Cre mice to PKM2fl/fl mice and (2) a pharmacological approach using currently available specific inhibitors for PKM2. It is envisioned that the successful completion of these studies will lead to a better understanding of the metabolic functions of PKM2 and may provide insights into therapeutic interventions for obesity and diabetes.